Thanks so much! Now, to be more specific, will the "usage" column tell me if the duplicated clips are all in one sequence or will it mean that every timeline that I have that uses the same clip will be listed?

Though you can click the triangle next to the number and find out which sequences the clip is used in, it's not quite as elegant as the forthcoming solution, which tells you right in the sequence and is usually the answer people are looking for when they ask this question.